Load lifting mechanism

ABSTRACT

A load lifting jack comprising a support member, a screw shaft rotatably located within the support member, a lifting arm supported at the substantially middle portion by a link and connected at its end to a threaded nut engaged with the screw, the nut being adapted to be displaced along the length of the screw shaft in order to raise or lower the lifting arm, the link being pivotally connected to the lifting arm at one end and having means for engaging the other end with any selected one of a plurality of recesses provided on the support member so that engagement thereof easily and quickly locates the lifting arm in its desired position. A rotatable jack base may be provided for lifting inclined loads to prevent undesired lateral movement of the load lifting jack.

United States Patent Yamazaki [451 Sept. 26, 1972 [73] Assignee: AisinSeiki Kabushild Kaisha,

Kariya,Japan 22 Filed: Jan. 12,1970

[21] Appl.No.: 2,319

[30] Foreign Application Priority Data FOREIGN PATENTS OR APPLICATIONS1,082,067 9/1967 Great Britain...;. ..254/l26 Primary Examiner-Othell M.Simpson Attorney-Pierce, Scheffler and Parker [57] ABSTRACT A loadlifting jack comprising a support member, a screw shaft rotatablylocated within the support member, a lifting arm supported at thesubstantially middle portion by a link and connected at its end to athreaded nut engaged with the screw, the nut being adapted to bedisplaced along the length of the screw shaft in order to raise or lowerthe lifting arm, the link being pivotally connected to the lifting armat one end and having means for engaging the other end with any selectedone of a plurality of recesses provided on the support member so thatengagement thereof easily and quickly locates the lifting arm in itsdesired position. A rotatable jack base may be provided for liftinginclined loads to prevent undesired lateral movement of the load liftingjack.

6 Claims, 6 Drawing Figures LOAD LIFTING MECHANISM This inventionrelates to load lifting jacks, and more particularly relates to jackswhich employ a load lifting arm of the cantilever type.

conventionally, there have been presented lifting devices of the abovegenerally indicated type which comprise a support member having a groundengaging member, a screw shaft rotatably mounted within the supportmember, a lever-type lifting arm mounted on a bush engaged with thescrew, and a link pivotally connected to the arm at one end and to theground engaging member at its other end. In operation, by rotation ofthe screw shaft the engaged bush is displaced along the length of thescrew and in consequence the end of the lifting arm is pivoted about itsinterconnection with the link. This construction is undesirable becauseit is necessary to raise the lifting arm from its completely collapsedposition until the load engaging member of the arm reaches a desiredposition adjacent the load by continuous manual rotation of the screw,and it is necessary to lower the arm from its lifted position also bycontinuous manual operation to collapse the device. This requiresconsiderable time and trouble throughout the raising and loweringmovement of the arm.

Therefore, itis a principalobject of the present invention to overcomethe above difficulties by providing improved jacking means of the abovetype which are simple in construction, economical to manufacture andefficient in operation.

According to this invention, briefly summarized, there are providedseveral recesses or detents on the support member or the jack basemember and leg means on the link for engagement with any selected one ofthe recesses. Engagement of the leg means and a recess locates thelifting arm at or near its desired position without rotation of thescrew shaft and disengagement thereof lowers the lifting arm readily andquickly.

Other objects will become apparent to those skilled in the art from thefollowing description with reference to the accompanying drawings whichdepicts preferred embodiments of the invention for illustrative purposesonly. I

In the drawings:

FIG. 1 is a side elevation of a jack in its collapsed position embodyingthe invention;

FIG. 2 is a view similar to FIG. 1 in its elevated position;

FIG. 3 is a view in vertical section, taken along the line III-III ofFIG. 2;

FIG. 4 is a plan view of the structure of FIG. 1;

FIG. 5 is a view similar to FIG. 1, but showing a modified form of thisinvention; and

FIG. 6 is a view corresponding to FIG. 4 of the structure of FIG. 5.

Referring first to the embodiment of FIGS. 1 to 4, the lifting devicecomprises generally a support or casing member 10 of upwardly openchannel form, and a load lifting arm 12 which carries at one end a loadlifting member 14 pivotally connected thereto by a pin 15. The liftingarm 12 which may be formed, for example, of relatively heavy gauge sheetmetal is movable between the fully collapsed position (FIG. I) in whichthe arm occupies a substantially horizontal position and the elevatedposition in which the arm may be substantially at right angle to thesupport member 10. An intermediate portion of the lifting arm has anenlarged cross sectional area since it receives the maximum bendingmoment. A jack base 16 is securely attached by welding, for instance, toone end of the support member 10. The base consists of a bottom member13 secured to the member and a pair of flanges 17 at opposite sides ofthe base which are substantially at right angle to the bottom member 13and are formed integrally therewith. There are provided, symmetrical tothe axis of the support member 10, several, three in this embodiment,recesses or detents 18 on the upper portion of each flange.

A screw shaft 20 is rotatably mounted within the support member 10. Arotary driving head 22 is fixed at one end of the shaft 20 and outsideof the support 10, at which a suitable driving handle (not shown) may beengaged so as to rotate the driving screw 20. A traveler nut 24 isinternally screw-threaded and carried on the screw shaft 20 at its otherend. The nut 24 includes a pair of cylindrical projections 26 and 28extending horizontally relative to the screw shaft 20, to act as pivotsfor a pair of rollers 30 and 32 which are rotatably mounted within thesupport member 10, respectively. A pair of forks 31 and 35 are providedat the lower end of the lifting arm 12 and formed integrally therewith.The forked portions 31 and 35 are positioned on opposite sides of thedriving nut 24 and between the rollers 30 and 32, and are also pivotallymounted on the cylindrical projections 26 and 28, respectively.

A thrust bearing 36 is attached on the screw shaft 20 between an endwall 37 of the support 10 and the rotary driving head 22. This bearingreceives the leftward thrust on the screw when in use as shown in FIG.2. A stopper ring 38 fixed to the screw 20 and in contact with the endwall 37, prevents the driving screw from being displaced axiallyrelative to the support member 10. It will be apparent that when thescrew is rotated the nut 24 is displaced along the length of the screwshaft 20 and is, smoothly guided along the inner wall of member 10 bythe rollers 30 and 32.

A link shaft in the form of a bifurcated member 40 is pivotally mountedat its central portion 42 in a recess 41 provided in the intermediateportion of the lifting arm 12 by supporting plates 44 and 46 securedthereto. A pair of leg portions 48 and 50 at the free ends of the link40 project outwardly in mutually opposite directions relative to themember 10 and are engageable with any selected one of the notches 18.When the lifting device is in its fully collapsed position, the legsengage the outer recesses 52 as shown in FIG. 1 or 4. When anintermediate height is desired, the legs are located at second recesses54 whereby the load lifting arm 12 is elevated about the projections 26and 28 as shown in FIG. 2. In order to elevate a vehicle 56, forexample, screw 20 may be rotated in a direction to cause traveler nut 24to advance to the right in FIG. 2.

It should be recognized that such construction causes less movement ofthe driving nut than would be the case if there were provided norecesses on the jack base member for receiving the leg members of thelink shaft.

In lowering the jack, a reverse action of course takes place. That is tosay, after revolution of the screw 20 in the opposite direction untilthere is no load on the load engaging head 14, the leg members 48 and 50are moved to the outer recesses 52 to cause the lifting arm 12 to besubstantially collapsed and parallel with the screw shaft 20 without anyfurther rotation of the screw 20.

Referring to FIGS. 5 and 6, there is shown a modification with the sameparts as shown in the previous embodiment being designated with the samereference numerals with primes affixed thereto.

The present invention relates also to a modified lift ing jackwhich-comprises a support member and the jack base 16'. The support 10'is pivotally mounted at one end on the base 16' by a pivot pin 56preferably with collars 58 'and 60 so that when the load engaging member14 is inclined to the horizontal because of.

inclination of the vehicle (not shown) the support member 10 is pivotedabout the pin 56. The pin 56extends across and is supported by theflanges 17' of the base 16'. It is to be noted that unless the supportmember 10 is pivoted according to the inclination of the vehicle, thesupport with the jack base will slide along the ground in the horizontaldirection.

The screw shaft 20' is rotatably mounted within the support l0'-. Therotary driving head'22' of the screw shaft 20'v is mounted at the otherend of the casing 10' with the thrust bearing 36'. A bearing member 62for the driving screw 20' is mounted within one end portion of thesupport 10' by rivets 64 and 66. The forked ends3land 35 of the loadlifting arm 12' are pivotally connected to the projections 26' and 28'of the internally threaded nut 24', which is located on the screw 20' atthe opposite end relative to the bearing member 62. A ground engagingmember. 68 may be fixed, by

lifting arm 12 as best shown in FIG. 6. Opposed ends of each pin aresecurely fitted in tubular members 74 and 76, respectively. Moreparticularly, legs 48 and 50 extend inwardly in mutually oppositedirections and are rigidly fitted in the tubular member 74, while thestems 42' and 42' of each pin are rigidly mounted in the tubular member76 and are pivotally connected to the lifting arm 12' at itssubstantially intermediate portion. it will be recognized that the abovestructure of the link shaft 40' ensures its rigidity and theengagementof the legs48' and 50' and the recesses 18' on the base member16' in comparison with that of the previous embodiment wherein the leg48 or 50 may be disengaged in the inward direction. v

The description of operation of the modified form will be omitted sinceit is substantially similar to that of V the first embodiment. I

It will be apparent to those skilled in the art that the detents orrecesses may be provided at one end portion of the support member-inplace of providing them on the flanges of jack base.

It is to be understoodthat the novel structure disclosed herein is notlimited in application to a vehicle but is also useable in anyapplication wherein the load is required to be liftedby m nual oeration.

The use and operation 0 the a vantages of the load thereof, said nutbeing'mounted on said screw shaft, a

along said screw shaft thus causing said load engaging member to beraisedv or lowered, the improvement wherein the other endof said linkshaft includes leg means and wherein said jack base is provided with apluralityof recesses spaced along the length thereof for selectivelyreceiving said leg means so that said load engaging member may be raisedto. a desired position adjacent the load to be raised before the screwshaft is rotated.

2. A load lifting jack as claimed in claim 1, wherein said jack base ispivotally mounted on saidsupport member.

3. A load lifting jack as claimed in claim 2, and further comprising adriving head secured to one end of said screw shaft and extendingoutside said support 7 member for rotation thereof.

4. A load lifting jack as claimed in claim 3, and further comprising aground engaging member disposed substantially at the middle of saidsupport member.

5. A load lifting jack as claimed in claim 1 and further comprising astop ring secured to said screw shaft for abutment against the inside ofone end of said support member so that axial displacement of said screwshaft relative to said support member when said screw shaft is rotatedwill be substantially eliminated.

6. A load lifting jack as claimed in claim 1, wherein said link shaftcomprises a pair of U-shaped members symmetrically arranged in abutmentto each other.

1. In a load lifting jack having a support member, a jack base attached thereto, a screw shaft rotatably mounted within said support member, a load lifting arm having a load engaging member at one end thereof and a threaded nut pivotally mounted on the other end thereof, said nut being mounted on said screw shaft, a link shaft pivotally connected at one end thereof to said load lifting arm and displaceably mounted at the other end to the support member, whereby when said screw shaft is rotated said threaded nut will be displaced along said screw shaft thus causing said load engaging member to be raised or lowered, the improvement wherein the other end of said link shaft includes leg means and wherein said jack base is provided with a plurality of recesses spaced along the length thereof for selectively receiving said leg means so that said load engaging member may be raised to a desired position adjacent the load to be raised before the screw shaft is rotated.
 2. A load lifting jack as claimed in claim 1, wherein said jack base is pivotally mounted on said support member.
 3. A load lifting jack as claimed in claim 2, and further comprising a driving head secured to one end of said screw shaft and extending outside said support member for rotation thereof.
 4. A load lifting jack as claimed in claim 3, and further comprising a ground engaging member disposed substantially at the middle of said support member.
 5. A load lifting jack as claimed in claim 1 and further comprising a stop ring secured to said screw shaft for abutment against the inside of one end of said support member so that axial displacement of said screw shaft relative to said support member when said screw shaft is rotated will be substantially eliminated.
 6. A load lifting jack as claimed in claim 1, wherein said link shaft comprises a pair of U-shaped members symmetrically arranged in abutment to each other. 